1. Field of the Invention
The present invention relates to an arrangement for two-dimensional DPCM coding comprising a controlled quantizer and comprising a quantizer controller to which the most-recently calculated picture element signal value and the adjacent picture element signal values of the preceding television line are respectively supplied.
2. Description of the Prior Art
It is standard in the transmission of color television signals to split the color signal into a luminance signal and two chrominance signals or, respectively, color difference signals. Differential pulse code modulation (DPCM) is frequently employed for data reduction in the transmission of the individual components. After initial experiments with a one-dimensional DPCM coding, the calculation of the assessed value for the determination of the DPCM signals was expanded by a vertical prediction. In comparison to the one-dimensional DPCM process, this two-dimensional DPCM process yielded a noticeable quality enhancement of the transmitted television pictures by way of a corresponding coding of both the luminance and the chrominance.
A control of the quantization dependent on the activity, i.e. dependent on the contrast between corresponding picture elements of successive television pictures was investigated in the dissertation "Optimierung von Farbfernseh-DPCM-Systemen unter Berucksichtigung der Wahrnehmbarkeit von Quantisierungsfehlern", by Peter Pirsch at the Technische Universitat, Hannover, 1979. The introduction of this controlled quantization in two-dimensional DPCM usually produced an additional improvement in the pictures in the luminance path. Insofar as reasons of expense are not in opposition, controlled quantization can, of course, also be employed in the case of chrominance signals. The effects of controlled DPCM were simulated in a data processing system. Teachings to a technically-feasible realization are, however, lacking.